Spiral balloon catheter

ABSTRACT

The present invention provides a balloon catheter system comprising one or more conduits to which are attached an inner compliant balloon having a non-helical shape in its deflated state, said balloon being enclosed by an outer non-compliant or semi-compliant balloon, wherein the inner balloon is constructed such that upon inflation, said inner balloon is capable of adopting a spiral or helical conformation. The present invention also provides methods for using said balloon catheter system.

FIELD OF THE INVENTION

The present invention relates to a balloon catheter device for use in the aspiration of thrombi and other particulate matter from body passages. More specifically, the presently-disclosed invention is a catheter device comprising an inner balloon that adopts a spiral conformation upon inflation, and a second, sleeve-like outer balloon.

BACKGROUND OF THE INVENTION

The inappropriate and undesirable formation of blood clots intravascularly may have severe pathological consequences, as a consequence of the disturbance of blood flow to vital organs and tissues such as the heart muscle and brain. In extreme cases, total occlusion of the afferent arteries may lead to ischemic damage which, in the case of the heart, may manifest itself clinically in the form of myocardial infarction. Similarly, the local production of thrombi in the cerebral vessels or the deposition therein of thrombotic emboli may lead to cerebral infarcts. In both cases, serious morbidity and death are common consequences. It has been estimated, for example, that emboli arising from atherosclerotic plaques of the carotid artery cause approximately one quarter of the 500,000 strokes that are recorded annually in the United States.

Several different medical and surgical approaches aimed at removing thrombotic and embolic material from blood vessels have been proposed and attempted. One such approach requires the injection of thrombolytic agents. Alternatively or additionally, a variety of balloon catheter systems have been used to both expand blood vessels that have become narrowed due to thrombus formation or deposition and, in some cases to collect detached thrombotic material and remove same from the body.

One example of a balloon catheter system that has been designed for use in removing thrombotic material and other intravascular particulate matter from the body is that disclosed in U.S. Pat. No. 4,762,130 (Fogarty). While several different embodiments of the catheter are described in the patent, a feature common to all of these embodiments is that a balloon is advanced into the region of the thrombus to be treated and then expanded into a helical or spiral configuration, thereby engaging said thrombus within the spiral channels of the inflated balloon. The spiral balloon is then withdrawn from the body with the thrombus still attached thereto. A particular disadvantage of this prior art system is that the catheter is usually inflated distally to the thrombus (or other particulate matter) and is then pulled back in order to facilitate collection of the thrombotic material by the balloon. This procedure can be traumatic for the blood vessel. Furthermore the balloon does not always completely seal the vessel and some of the debris escapes into the blood stream and is not removed. A further key problem associated with this system is the fact that during balloon inflation, the blood flow through the vessel is blocked.

It is a purpose of the present invention to provide a balloon catheter system that may be used for trapping and retaining particulate matter and safely removing said matter from the body.

It is a further purpose of the invention to provide a balloon catheter system that overcomes the problems and disadvantages associated with prior art devices.

Further objects and advantages of the present invention will become apparent as the description proceeds.

SUMMARY OF THE INVENTION

The present invention is a balloon catheter device that uses a spiral balloon as an aspiration device. The device is composed of a catheter fitted with two balloons, one inside the other.

The present invention is primarily directed to a balloon catheter system comprising one or more conduits to which is/are attached an inner compliant balloon having a non-helical shape in its deflated state and an outer non-compliant or semi-compliant balloon, such that said inner balloon is enclosed by said outer balloon, and wherein the inner balloon is constructed such that upon inflation, said inner balloon is capable of adopting a spiral or helical conformation. The catheter system is further characterized in that the outer balloon is perforated by a first set of pores or openings along most or all of its surface, and is further perforated by a second set of pores or openings in the regions of the proximal neck or taper of said outer balloon, wherein the pores or openings of said second set are significantly fewer in number and larger in diameter than said first set.

For the purposes of the present disclosure, the terms “proximal” and “distal” are defined from the physician's (or other operator's) perspective. Thus, the term “proximal” is used to refer to the side or end of a device or portion thereof that is closest to the external body wall and/or the operator, while the term “distal” refers to the side or end of a structure that is in an opposite direction to the external body wall and/or operator.

In one preferred embodiment the distal and proximal necks of the inner and outer balloons are attached to a single catheter conduit. In another preferred embodiment, the distal necks of the inner and outer balloons are attached to one catheter conduit while the proximal necks thereof are attached to a second conduit, wherein said first and second conduits are arranged such that at least a portion of the shaft of one of the conduits is disposed within the lumen of the other conduit.

In another aspect, the present invention is directed to a method for removing particulate matter from a body passage in a patient in need of such treatment, comprising the steps of:

-   -   a) providing a catheter fitted with an inner compliant balloon         and an outer semi-compliant or non-compliant balloon as         disclosed hereinabove, wherein the outer balloon is perforated         by a first set of pores or openings along most or all of its         surface, and is further perforated by a second set of pores or         openings in the regions of the proximal neck or taper of said         outer balloon, wherein the pores or openings of said second set         are significantly fewer in number and larger in diameter than         those of said first set;     -   b) introducing said catheter into a peripheral blood vessel and         advancing same until the balloons are located in the region of         the particulate matter to be removed;     -   c) partially inflating the inner balloon to a first expanded         state such that the inner balloon adopts a spiral conformation         and such that a spiral channel is formed between said spiral         balloon and the outer balloon, said channel becoming filled with         particulate matter that has entered said spiral channel through         the aforementioned second set of pores located in the region of         the proximal neck of said outer balloon;     -   d) further inflating the inner balloon to a second expanded         state, such that the proximal coils of the spiral-shaped inner         balloon block the aforementioned openings in the outer balloon         and reduce the volume of the spiral channel formed in step (c),         thereby causing the outward passage of particulate matter of a         size smaller than the average diameter of the first set of pores         through said pores, but retaining particulate matter of         particulate matter of a size larger than said average diameter         in the reduced space between the inner and outer balloons;     -   e) partially deflating the inner balloon to the aforementioned         first expanded state such that further particulate matter may be         received in the spiral channel;     -   f) repeating steps (d) and (e)as required until sufficient         particulate matter has been accumulated in the space between the         inner and outer balloons; and     -   g) completely deflating the inner balloon and withdrawing the         catheter from the patient's vasculature with the particulate         matter trapped between the inner and outer balloons.

In the above-described method, the phrase “in the region of the particulate matter to be removed” is intended to convey the meaning that the balloons may be located at any of the following locations: entirely proximal to the debris, entirely distal to the debris, entirely within the region of the debris or partially within and partly without (distal or proximal to) the region of the debris.

In a preferred embodiment of the above-disclosed method, the particulate matter to be removed is thrombotic material.

In another embodiment of the device of the invention, said device further comprises a layer of an absorbent material surrounding the inner balloon in an annular manner. While any suitable absorbent material may be used for this purpose, in a preferred embodiment, said material is selected from the group consisting of steel wool and fibrous polymers. Unlike the embodiments of the device described hereinabove, the presently-disclosed device does not have an open spiral channel when the inner balloon is inflated. Rather, said spiral channel is obliterated by the present of the absorbent material. Thus, rather than trapping particulate matter within the spiral channel as described above, in the presently-disclosed embodiment, the thrombotic debris and/or other matter is absorbed within the pores of the absorbent layer.

All the above and other characteristics and advantages of the present invention will be further understood from the following illustrative and non-limitative examples of preferred embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts the balloon catheter of the present invention with the inner and outer balloons in their collapsed, deflated states.

FIG. 2 illustrates the balloon catheter of the present invention following the first stage of inflation of the spiral balloon.

FIG. 3 illustrates the balloon catheter of the present invention following full inflation of the spiral balloon.

FIG. 4 shows a short-axis cross section of the balloon catheter of the present invention with the spiral balloon in its partially inflated state.

FIG. 5 shows a short-axis cross section of the balloon catheter of the present invention with the spiral balloon almost fully inflated.

FIG. 6 represents a short-axis cross section of the balloon catheter of the present invention at the proximal end of the spiral balloon.

FIG. 7 shows a longitudinal section of a spiral-forming balloon (deflated) mounted on a single-lumen stainless steel tube.

FIG. 8 shows a longitudinal section of a spiral-forming balloon (deflated) mounted on a guidewire state having a sliced distal portion.

FIG. 9 depicts a longitudinal section of a spiral-forming balloon (deflated) having a stainless steel wire welded to the distal end of a stainless steel conduit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is based on the use of an inner compliant balloon which is fitted over a conduit and covered with a second, outer non-compliant or semi-compliant balloon. In its deflated state (FIG. 1), the inner balloon is in the form of a tube of compliant material with a diameter, in one preferred embodiment, of up to 1/15 of the final crossing profile of the inflated balloon. The tube can be constructed with a uniform wall thickness or with a wall thickness which varies along its length. The collapsed inner balloon together with the outer balloon that surrounds it are jointly indicated in FIG. 1 by part number 12 attached to catheter shaft 10.

The inner balloon can be made from one material. Alternatively, the inner balloon may be constructed from two or more different materials, thereby producing a non-uniform spiral balloon upon inflation. Suitable materials for use in constructing the inner balloon include (but are not limited to): silicones and thermoplastic elastomers (TPEs).

The inner balloon 12 is bound at two points to a rigid or semi-rigid conduit 10 which is threaded through the balloon. Since the balloon is made of a compliant material it elongates during inflation. However, as the inner balloon 12 is bound at both its ends, its longitudinal elongation is restrained. Provided certain balloon-related design parameter criteria are met (as will be discussed hereinbelow), said inner balloon 12 will then buckle and assume a spiral shape as shown in FIGS. 2 and 3. As seen in these figures, the outer balloon 14 (perforated with small pores 16) completely surrounds the inner balloon 12. The proximal end of the outer balloon is indicated by the letter P in FIG. 2.

It has been unexpectedly found by the present inventors that certain fundamental conditions need to exist in order for the compliant, inner balloon of the present invention to adopt a spiral or helical shape when inflated. These may be summarized as follows:

-   -   1. For a specific balloon dimension the balloon material should         have a minimum value of elongation (E).     -   2. For a given specific balloon dimension and a specific         elongation of the material a minimum initial length of tube (L₀)         is necessary.     -   3. The compliant balloon tube should be assembled on a stiff         core shaft that withstands the longitudinal spiral forces.         Otherwise the core will elongate and the spiral balloon will         become a spherical balloon.     -   4. The balloon tube should be attached at both ends to the stiff         core shaft so that its longitudinal elongation is restricted.     -   5. Minimum radial uniformity of the wall thickness of the         balloon tube is necessary to form a spiral balloon.     -   6. Minimum homogeneity of the balloon material is necessary to         form a spiral balloon.     -   7. The space between the outer surface of the shaft and the         inner wall of the compliant tube (“t”) should allow relative         movement of the compliant tube over the core shaft during         inflation. If the space is too small or non-existent, the         friction between the balloon and the shaft does not allow an         even elongation of the tube and the formation of a spiral shape.

Thus, only when the above conditions are met will a compliant balloon adopt a spiral conformation upon inflation. Examples of various compliant balloons and their ability to adopt a spiral conformation are summarized in the Example provided hereinbelow.

Using different wall thicknesses or different materials the shape of the helix and the inflation sequence can be controlled. In this regard, the inventors have unexpectedly found that the ratio between the diameter of the inner balloon in its unexpanded state, the length of said balloon and the thickness of its wall is an important determinant of the ability of the compliant inner balloon to expand from a tubular shape into a spiral or helical conformation. In one preferred embodiment, for example, it has been found that a compliant balloon having a length of 30 mm, an outer diameter of 1 mm and a wall thickness of 0.25 mm readily adopts a spiral conformation upon inflation, provided that both ends of said balloon are bound to a rigid conduit.

Typically, the inner balloon will have a length in the range of 15mm to 50 mm and a wall thickness in the range of 100 micron to 400 micron. It should be emphasized that the preceding dimensions (and all other dimensions that appear herein) are exemplary values only, and should not be construed as limiting the size of the presently-disclosed device in any way.

The inner, spiral balloon 12 in its inflated state creates a spiral channel 17 surrounding it, which allows free flow through the channel. The shape and size of the cross-section of the spiral channel 17 can be varied from a very small cross-section area (when the balloon is fully inflated, FIG. 5) to 70-80% (when partially inflated, FIG. 4) of the balloon cross-section area.

The spiral balloon is covered with a non-compliant or semi-compliant balloon which is bound to the same shaft as the spiral balloon.

The outer balloon may be constructed of any suitable non-compliant or semi-compliant material, including (but not limited to): nylon, Pebax, polyurethane and polyethylene terephthalate (PET).

The outer balloon is perforated along most of its lateral surface by a first set of holes or pores 16 (FIG. 2) of a pre-determined size, whereas a second set of pores 20 perforates the proximal taper or neck of said outer balloon, said pores 20 being fewer in number but having a larger diameter than the holes of the aforementioned first set (FIG. 6). When the inner balloon is in its deflated state, the outer balloon is folded on top of the spiral balloon to create a reduced cross-section profile. Upon active inflation of the inner balloon, the outer balloon passively expands as a result of the outward pressure exerted by the inflated or partially inflated spiral balloon.

The general embodiment of the balloon catheter of the present invention that is described hereinabove and depicted in FIGS. 1-3 comprises a single catheter conduit to which is attached both the inner and outer balloons. However, it is to be recognized that many other catheter conduit conformations may also be used in the present invention. For example, instead of the single-conduit system, the device of the present invention may have a two-conduit conformation, with (for example) the proximal necks of the inner and outer balloons being attached to the outer surface of an outer conduit, while the distal necks thereof are attached to the outer surface of an inner conduit that is disposed within the lumen of said outer conduit. In this type of conformation, the inner conduit will generally extend beyond the distal end of the outer conduit. The device of the present invention may also comprise one or more conduits having multiple lumens (e.g. bi-lumen catheters) where the additional lumens may be used for a variety of purposes, including the passage of guidewires, instrumentation or tools.

In addition, various catheter tubes having a particularly small cross-sectional profile may be used to mount the spiral-forming balloon of the present invention. In one preferred embodiment, the catheter is constructed of a single-lumen stainless steel tube with a distally assembled spiral balloon (FIG. 7). The deflated cross profile ranges between 0.4 and 0.8 mm. The tube may be delivered to the target through a 2.4 Fr or 3.8 Fr microcatheter. The catheter tube 18 can have a laser cut (spiral cut or grooves) at its distal section or all along its length to increase its flexibility. In order to maintain the integrity of the lumen, a thin (approximately 0.0005) polymeric jacket 19 (for example, PET or PTFE) is applied over the tube (e.g. by a heat-shrink process). An aperture 26 is created at the distal section of the hypotube for the inflation of the spiral balloon. The distal end of the hypotube 28 is plugged by using a plasma weld process, laser weld process or adhesive process. The compliant balloon 24 is shown in this figure and in the figures that follow in its deflated state.

The aforementioned spiral-forming balloon is attached at its ends to the distal portion of the hypotube (in a non-spiral, conventional manner) by means of thermo-bonding or adhesive technology.

In a variant of this embodiment, as shown in FIG. 8, a reduced cross-section profile of the distal portion of the hypotube 20 (i.e. in the region of the balloon attachment) is obtained by longitudinally slicing said portion, thereby creating a reduced diameter tube region 22 of approximately semi-circular cross sectional form.

In a further reduced cross-section variant, shown in FIG. 9 a stainless steel wire 30 having a diameter of, for example, 0.2 mm may be welded to the distal end of the tube 20. As a result of this modification, a balloon 24 with a smaller ID may be used, thereby leading to a distal section having a significantly smaller cross section profile.

The conduits used to construct the catheter device of the present invention may be made of any suitable material including (but not limited to) a biocompatible polymer such as polyurethane or nylon or PET, or a biocompatible metal such as stainless steel, and may be manufactured utilizing conventional methods, such as extrusion and laser cutting. The diameter of the conduits is generally in the range of 0.5-2.0 mm, and their length is generally in the range of 100-2000 mm.

The compliant inner balloon may be inflated by introducing a pressurized inflation media via an inflation fluid port that is in fluid connection with a source of pressurized media and a pumping device or syringe. In the case of a single conduit catheter, the inflation media passes through openings in the wall of the catheter shaft located between the proximal and distal attachment points of the balloon. In the case of a dual (inner-outer) conduit conformation, as described above, the inflation media passes via an inflation fluid lumen formed between the inner wall of the outer conduit and the outer surface of the inner conduit.

Typical Procedure for Using the Balloon Catheter of the Present Invention:

-   -   1. The catheter is advanced through the target blood vessel         until the balloons are delivered distally to the aspiration         target.     -   2. The inner balloon is partially inflated to a first pressure         and the outer balloon passively expands and spreads over said         inner balloon. A spiral channel is formed between the inner         balloon (which has now adopted a spiral or helical form) and the         outer balloon. This channel fills with both particulate matter         and blood situated proximal to the balloon through the large         openings located in the proximal taper of the outer balloon. The         presence of the smaller pores along most of the lateral surface         of the outer balloon, together with the formation of the         aforementioned spiral channel, permits continued blood flow in         the vessel. The outer balloon functions as a filter and traps         debris within the spiral cavity.     -   3. Further inflation of the balloon causes the proximal coils of         the spiral balloon to block the large openings located at the         proximal neck of the outer balloon and reduce the volume of the         spiral channel, thereby squeezing a portion of the material         through the small perforations in the outer balloon.     -   4. Partial deflation recreates the spiral channel which         continues to fill with new portions of matter (blood and         particulate matter).     -   5. Step 3 and 4 can be repeated several times.     -   6. When the clinical need is met, the spiral balloon is         completely deflated and retrieved through the guiding catheter         and the debris is trapped inside the outer balloon.

By way of further explanation, it should be noted that the filtering and trapping function of the outer balloon mentioned and described in steps 2 and 3, above, is related to the size of the pores formed along most of the surface of the outer balloon (“small pores”), as well as the size of the larger pores situated at the proximal neck of the outer balloon (“large pores”). Thus, particulate matter having an average diameter less than the average diameter of the large pores will be able to enter the space between the inner and outer balloons. Any particles larger than the size of these pores will not be able to enter into that space. Once inside the space between the inner and outer balloons, and following the further expansion of the inner balloon and blockage of the large pores described in step 3, above, any particles smaller than the small pores will be squeezed out through said small pores and thereby returned to the bloodstream. Conversely, all particles larger than the small pore diameter will be retained in the space between the outer and inner balloons and ultimately removed from the body together with the catheter. It will therefore be appreciated that the outer balloon performs the following three key functions:

-   -   filtration of solid or semi-solid particles suspended in blood;     -   pumping of the blood and particulate matter smaller than the         small pores back into the bloodstream; and     -   entrapment of large debris having a size greater than the small         pores.

The pressure in the balloon after partial inflation to a first expanded state (as described in step 2, above) is in the range of 0.5 to 10 atmospheres.

All of the abovementioned parameters are given by way of example only, and may be changed in accordance with the differing requirements of the various embodiments of the present invention. Thus, the abovementioned parameters should not be construed as limiting the scope of the present invention in any way.

Example Influence of Key Balloon Parameters on Their Ability to Adopt a Spiral Conformation

The following table summarizes certain key parameters of a series of different compliant balloons which were bound at both ends to a rigid catheter (diameter 0.3 mm). In the cases in which a spiral conformation was not achieved following inflation with water, this fact is mentioned in the ‘comments’ column of the table:

Number % of Spiral Elongation OD ID L₀ Threads Balloon Balloon Material at break [mm] [mm] [mm] (N) OD [mm] Comments TPE* 510 0.8 0.4 20 3 4.5 TPE 510 0.9 0.5 20 3 5.5 TPE 700 0.8 0.4 20 2.5 7.5 Silicone 373 0.8 0.4 20 4 4 Silicone 373 0.6 0.3 20 N/A N/A Spiral balloon was not formed due to no space between the ID of the balloon and the OD of the shaft. Silicone 373 0.8 0.4 7 N/A N/A A spiral balloon was not formed. The initial length was too short. Polyurethane 50 0.8 0.4 20 N/A N/A A spiral balloon was not formed due to an elongation which was too low. *The TPE used in this study was Evoprene Super G 948 (Alpha Gary Company)

It will be seen from the proceeding table that only the balloons characterized by having certain structural parameters (e.g. length, diameter, material etc.) are capable of adopting a spiral conformation upon inflation.

While specific embodiments of the invention have been described for the purpose of illustration, it will be understood that the invention may be carried out in practice by skilled persons with many modifications, variations and adaptations, without departing from its spirit or exceeding the scope of the claims. 

1. A balloon catheter system comprising one or more conduits to which are attached an inner compliant balloon having a non-helical shape in its deflated state, said balloon being enclosed by an outer non-compliant or semi-compliant balloon, wherein the inner balloon is constructed such that upon inflation, said inner balloon is capable of adopting a spiral or helical conformation, and wherein said outer balloon is perforated by a first set of pores along most or all of its surface, and is further perforated by a second set of pores or openings at the proximal neck thereof, wherein the pores of said second set are significantly fewer in number and larger in diameter than said first set.
 2. The balloon catheter system according to claim 1, wherein the inner and outer balloons are attached to a single catheter conduit.
 3. The balloon catheter system according to claim 1, wherein the distal necks of the inner and outer balloons are attached to one catheter conduit while the proximal necks thereof are attached to a second conduit, wherein said first and second conduits are arranged such that at least a portion of the shaft of one of the conduits is disposed within the lumen of the other conduit.
 4. The balloon catheter system according to claim 1, further comprising an annular layer of an absorbent material surrounding the inner balloon.
 5. A method for removing particulate matter from a body passage in a patient in need of such treatment, comprising the steps of: a) providing a catheter system according to claim 1, wherein the outer balloon of said catheter system is perforated by a first set of pores along most or all of its surface, and is further perforated by a second set of pores or openings at the proximal neck thereof, wherein the pores of said second set are significantly fewer in number and larger in diameter than said first set; b) introducing said catheter into a peripheral blood vessel and advancing same until the balloons are located in the region of the particulate matter to be removed; c) partially inflating the inner balloon to a first expanded state such that the inner balloon adopts a spiral conformation and such that a spiral channel is formed between said spiral balloon and the outer balloon, said channel becoming filled with particulate matter that has entered said spiral channel through said second set of pores; d) further inflating the inner balloon to a second expanded state, such that the proximal coils of the spiral-shaped inner balloon block the second set of pores and reduce the volume of the spiral channel formed in step (c), thereby causing the outward passage of particulate matter of a size smaller than the average diameter of the first set of pores through said pores, but retaining particulate matter of particulate matter of a size larger than said average diameter in the reduced space between the inner and outer balloons; e) partially deflating the inner balloon to the first expanded state described in step (c), such that further particulate matter may be received in the spiral channel; f) repeating steps (d) and (e) as required; and g) completely deflating the inner balloon and withdrawing the catheter from the patient's vasculature with the particulate matter trapped between the inner and outer balloons.
 6. The method according to claim 5, wherein the particulate matter to be removed is thrombotic material. 